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Topic: PVC collars (Read 6351 times)

Hi All , just some photos of a job I have just been doing , a friend needed some PVC collars making that fit on a driven shaft to mix paint or some type of job like that. Anyway he gave me one to copy and this is what it involved. There is probably lots of ways it could have been done other than this but it is partly working around what gear is able to be reached and what gear is actually working and not needing fixed lol. Its 100mm solid PVC bar , so first job is to cut into decent sized bits for the lathe, I did this on the big bandsaw.

Then mounted this bit into the Binns and Berry lathe, center drilled the end, supported with revolving centre, and skimmed the outer surface until true and round. Its extruded bar so not that perfect to start with. I then draw the tool along the length so it has a scribed center height line for use later.

It was then drilled out with large drill a couple of mm under the final bore size, makes plenty shavings !

Next stage is to part off slightly too long as the parting tool leaves rough finish on both the part and the bar left in the chuck, so each part needs skimmed to size which will leave decent finish too.

I then did one test bore to get the right size for the sample shaft to fit then do each collar without touching the setting for the boring bar so they al match, then do the same with them all length wise too, by doing one , leaving the tool setting, then doing the rest without moving the settings.

Next there are two 6mm holes drilled through from flat side to flat side, these are 90 degrees out from a 8.5mm hole that goes straight through the collar from one side to the opther. I used the original sample collar to center punch through to mark the two spots by using a section of shaft mouted into a base plate as a jig also lining it up with the center line that was scribed when still on the lathe. The same jig is then used then used to set up on the drill press to drill the holes. The collar can be rotated around the shaft in the jig so the holes are both same radius from centre point, then drilled in line with dotted marks.

Next its the straight through hole of 8.5mm , I have experimented before with this and drilling straight through seems to wonder off so I go from each side into the center using a jig type set up on the bridgeport. First the angle plate is set so it puts the drill center line on the collar, then the V block and stop black make the collar locate, the scribed center line is then lined up with the line scribed on the angle plate at tool center line and each collar clamped and drilled.

Then to do the matching hole on the other side I set a plastic 8.5mm pin in a scrap bit of alloy and located it the set distance from the angle plate and again on the center line scribed to the drill center. using the hole already drilled , this locates over the plastic peg, the collar clamped then drilled, as I did them just tested with a pin that reached right through the collar.

Thats it job done, I know things could have been done more precise with rotary tables etc but these are just rough and ready items to attach discs that spin in paint to so , if they do the job , its mission accumplished. Cheers Mick.

Thanks Steve, it was late so I am surprised there was not lots of typos lol.

Hi Jonny , the mates rates works out ok as the lad I did them for does favours back so it all works out in the end.

Swarfing, well spotted , when I got the lathe there was a hole in headstock casting there where a belt driven coolant pump pipe was meant to come through, my mate when he seen the lathe says , ' by thats a big bastard ' so the lad that gave me the plate engraved on it, Binns & Berry Big Bastard

A drill will try and tear the workpiece out from the jaws of the chuck, it will even attempt to tear it out of a vise as well.

If you happen to sharpen the drill as you would for drilling brass, then this eliminates that pulling effect when drilling.You got to get rid of those sharp edges on the drill, as that is what tears into the plastic and frightens the bejesus out of you."As usual, there has to be some yank on you tube, extolling the virtues of "backing of the cutting edge" on the drill.

Andrew other than the yank bit, which I don't get, I think he's positive about the video, negative about the results of holding drill press work by hand (as is Tom), and using a conventionally sharpened bit on plastic or brass.

I'd disagree with both that "dulling' the bit is what is wanted, rather than reducing the cutting angle while keeping the bit edge sharp.

I usually reduce the angle to parallel with the bit axis, and use a bench stone -- keeping the bit parallel to the corner of the stone over which the lip is hooked. This adds a small edge parallel to the axis of the drill bit, but a sharp edge, not a dull one.

In Tom's video I see a slip used and the angle is varied as he uses it and calls it dulling or chamfering. It does work on plastic, but I think the scraping of a sharp edge (not a sharp angle) is faster and smoother cutting. One Yank's opinion anyway.

Hi Lads , just saw the comments about drill bits, the bit I used was what I thought was pretty sharp normal type grind to the point bit, I am not sure but this PVC is quite hard but not like perspex hard. As the drill bit goes in the material feels soft and soon the bit is warm and the shavings come out very soft and pliable soon returning to hard again but this might be why I had no snatching ? I was lucky as just thought here is a bit about the size I need , lets go for it I would agree with the angle getting altered but keeping the sharp edge if snatching was a problem. From the videos and other info I have seen from Tom, he seems the walk the walk not just talk the talk so I would think his advice will be effective too.